The impact of HPMC on external insulation systems

On the benchmark, HPMC can use various types of adhesives. At the beginning, the ready to use adhesive with polymer lotion as the base material was most widely used. However, this kind of adhesive will cause many quality problems due to improper operation on the construction site, especially when it is mixed with cement and water. The improper mixing ratio of polymer and cement often causes quality problems in HPMC construction. The same problem also exists when the two-component system is used (the mixture of polymer lotion and water will be mixed with cement and sand at the construction site). After theoretical proof, the use of polymer modified dry mixed mortar (i.e. single component system) is much superior to the use of dual component system, mainly manifested in the convenience of storage and transportation, as well as the reliability of construction. Due to the fact that various ingredients in the single component system were pre mixed in the factory, the occurrence of on-site mixing errors was completely prevented. Here, this article will stop introducing the impact of redispersible latex powder on the bottom layer performance of HPMC.

According to the draft European standard, the definition of the bottom layer is: it is a coating directly applied to the surface of the insulation material, including a reinforcing mesh. The bottom layer must be selected according to the system’s requirements. At the same time, it is pointed out that the bottom layer has a decisive impact on the mechanical performance of the HPMC system

To ensure sufficient technical performance, the bottom layer is usually modified by adding 3-6% redispersible latex powder. Redispersible emulsion powder can be made from polymer lotion through spray drying. This powder will be dispersed into the original lotion after mixing with water and play a role as a typical polymer adhesive. To ensure sufficient maintenance capability for an extremely thin (3mm) substrate, it is particularly important to participate in redispersible latex powder. After polymer modification, the bonding performance, deformation ability, and impact resistance of the protective layer have been improved, ensuring the long-term stability of the system. If the bottom layer is properly modified with redispersible latex powder, multiple materials can be selected as the decorative layer (such as organic synthetic coatings, silicone resin coatings, organic silicone coatings, and cement-based coatings). Considering the long-term stability of the entire system, the decorative layer coating should also be modified with redispersible latex powder to achieve mutual matching between the surface layer and the bottom layer.

In this regard, four different types of redispersible latex powders were used through experiments, and bottom layer test plates were made according to regular formulas to investigate the adhesion, hydrophobicity, mechanical stability, weather resistance, and other properties of the bottom layer and HPMC board. The four powders are: powder A is vinyl acetate ethylene copolymer (VAc/E), and powder B is ethylene Lauric acid ethylene chloride